Circuit maker and breaker



Jan. 2, 1945;

CIRCUIT MAKER AND BREAKER J. x. MATHIEU 2,366,542

Filed 0Qtf'2 2, 1942 v Inventor Joseph Mat hie u,

7 Hi 5 Attorney.

Patente'cl Jan. 2, 1945 CIRCUIT MAKER AND BREAKER Joseph X. Mathieu, Pittsfield. Mass., assignor to General Electric Company, a. corporation of New York Application October 22, 1942, Serial No. 462.946

Claims.

This invention relates to circuit makers and breakers and more particularly to an improved compound arcing duty contactor which is particularly adapted for use with a certain type of load ratio control circuit.

By load ratio control is meant the changing of the ratio of a transformer by tap-changing means without interrupting the transformer load current. In many load ratio control circuits the actual tap-changing orrati-o adjustin is done by means of non-arcing duty switches and the current interrupting or arcing duty is performed by separate switches. In a particular circuit of this type forming the subject matter of Patent No. 2,112,064, granted March 22, 1 938 on an application of L. F. Blume and assigned to the assignee of the present application, the arcing duty is performed by a compound switching arrangement utilizing a pair of non-arcing duty selector switches and a single arcing duty switch.

In accordance with this invention there is provided a novel and simple combination of arcing duty switch and non-arcing duty switches which is particularly adapted for use in the circuit of the Blume patent. It is characterized by a compact structure in which all of the switches are operated by a single cam and no more than two cam followers are employed. Furthermore, the arcing duty switch is a multir ak switch which actually consists of at least .Wo separate and distinct sets of contacts which open and close substantially simultaneously.

One advantage of a multi-break arcing duty.

switch is that it increases the current interrupting ability. Another advantage is that a suitable impedance, such, for example, as a resistor, may be connected in parallel with one set of arcing duty contacts so that the benefits of the novel resistor-saturable reactor switching described in a copending application of L. F. Blume, Serial No. 462,945, filed October 22, 1942 and assigned to the assignee of the present application may be obtained.

An object of the invention is to provide a new and improved compound circuit maker andv breaker.

Another object of the invention is to provide a i the following description taken in connection" selector with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 is a perspective view of an embodiment of the invention in which all of the switchesor pairs of contacts are closed and in which the electrical connections thereof in selector switches "open and the other selector switch closed.

Referring now to the drawing nd more particularly to Fig. l, a pair of terminals I and 2 are' connected respectively to separate contact fingers 3 and 4 of a non-arcing duty ratio adjuster-5' for a transformer whose multi-tapped winding is shown atdfi; interposed between each terminals and its associated contact finger is one-half of a split reactor 1. This comprises a pair of equal- It serves the dual purpose of an autotransformer for giving main windings one common core.

transformer circuit voltages intermediate the voltages of the separate taps and a reactor for preventing short circuiting of the tap--to-ta=p voltage of the winding 6.

Ordinarily it is desirable to keep all. arcing contacts for switches outside of the tank containing the windings and insulating liquid of a power transformer and to that end the terminals of the switching arrangement are mounted on insulating bushings 8 and 9 extending through openings in the transformer casing. Pivotally mounted on the terminals I and 2 are non-arcing duty selector switch arms I!) and H which are adapted to be moved into and out of engagement with fixed'contact terminals [2 and i3 respectively. These contacts are permanently con- 1 nected together to one conductor 14 of the main circuit for the winding 6, the other conductor of which is shown at 15.

For operating the movable contact arms if) and l I there is provided a cam 16 which by means of a. shaft IT is interlocked with the ratio adjuster 5 so that the two'are maintained in the proper relation to each other. Cam IB has equal radii in all directions and its face consists of a.

groove having an offset portion in the axial direc tion. Fitted in this groove along angularly displaced radii of the cam are a pair of rollers or cam followers l8 and [9 which are connected through suitable cranks and linkages 20 and 2!.

tothe respective switch arms 10 and H.

The cam I 6 has a normal position in which both of the switches lD-.l2 and I l-|3 areclosed.

A complete rotation of this cam from its normal position will open one switch and then reclose it, and then will open the other switch and then reclose the latter. the order in which the switches operate depending upon the direction of rota-- tion of the cam.

A feature of the above-described cam face and cam follower relationship is that the same portions of the cam face move both carn followers in the same direction. Thus, although the cam followers are displaced along substantially diametrically opposite radii of the cam, nevertheless the same portion of the cam face which causes downward movement of one cam follower also causes downward movement of its diametrically opposite follower and conversely the same portion of the cam face which causes upward movement of one cam follower causes upward movement of the other cam follower. This feature is used to cause operation of a multi-break arcing contactor by each of the cam followers.

The multi-break arcing duty contactor comprises a pair of arcing duty contact 22 and 23 carried respectively on pivotally mounted insulating arms 24 and 25. The contacts 22 and 23 are electrically interconnected by a conductor 26 and the insulating arms 24 and 25 which carry them are mechanically tied together by a rigid bar 27. The insulating arms are mounted on members 28 and 28 which are loosely mounted on the shafts of the respective cam followers i8 and I9. Springs 30 and 3| serve to bias the contacts 22 and 23 into engagement with their respective co-operating fixed contacts I and 2.

Each of the cam followers and their associated members 28 and 29 have interlocking projections 32 (shown more clearly in Fig. 2) whereby operation of the cam followers in the direction to open their associated non-arcing duty selector switches will, after those selector switches have first opened, cause simultaneous opening of the arcing duty contactor switches |-22 and 2-23. Continued rotation of the cam I6 will eventually cause reclosure of the non-arcing duty switches and the springs 30 and 3| will reclose the arcing duty contactor switches.

The operation of the illustrated embodiment of the invention is as follows: With the parts as shown in Fig. 1 all of the switches or cooperating pairs of contacts are closed so that the load current of the winding 6 divides substantially equally between the branch conductors or conducting paths to which the ratio adjusters 3 and 4 are respectively connected. The voltage difference between the taps to which the contact fingers 3 and 4 are connected causes a circulating current to flow through the path which, starting with the contact finger 3, may be traced as follows: The left-hand half of the split reactor 1, the selector switch lil3, the selector switch Iii-l2, the right-hand half of the split reactor 1, the contact finger 4 and back to the contact finger 3 through the main winding 6. This current is limited to a value which does not exceed the overload current rating of the winding 6 by the reactance of the split reactor, whose two windings are so arranged that they act cumulatively on their common core when such a circulatin current fiows.

The rotation of the shaft I! in one direction will cause the following sequence of operation. First the selector switch ll-l3 will open, then the multi-break arcing duty switch |22--232 will open, then the contact finger 4 will move to the left so as to make connection with the same tap to which the contact finger 3 makes contacts nection, then the arcing duty switch |22-232 will close and then the selector switch I l--l3 will close. This corresponds to one-half of a complete revolution for the cam l6. During the next half revolution the selector switch Ill-I2 will first open, then the arcing duty switch will open, then the contact finger 3 will move to the left into contact with the left-hand tap, then the arcing duty switch will reclose and finally the selector switch l0l2 will reclose. If, on the contrary, the shaft ll had been rotated in th opposite direction, then the selector switch l0-I2 would have first opened followed by the opening of the arcing duty switch and the movement of the contact finger 3 to the right into engagement with the same tap to which the contact finger 4 is shown as making connection. The selector switch l0|2 and the arcing duty switch would then reclose in the order mentioned. This would take place during the first. half revolution of the cam and during the second half revolution the selector switch lll3 would first open, then the arcing duty switch would open, then the contact fingeri 4 would move to the right into contact making relationship with the next right-hand transformer tap, then the selector switch |l--l3 and the arcing duty switch would reclose in the order mentioned. This covers a complete cycle of operation of the parts for either direction of operation of the shaft H.

Whenever either selector switch opens all the current flowing through it immediately transfers to the arcing duty switch so that the single arcin: duty switch serves to interrupt the current in each of the branch circuits as long as the appropriate selector switch has previously been opened. Consequently, the operation of th contact fingers 3 and 4 is carried out without any arcing as the circuits of these contact fingers have prea resistor 33 across either one of its sets of con- As shown, it is connected across the con- I-22. With this arrangement the are drawn between the contacts l-22 will go out before the arc drawn between the contacts 23-4 and the current in the are drawn between the contacts 23--2 will all flow through the resistor tacts.

26 as well as through one-half of the split reactor 1. This so changes the phase relation between the arc current and the arc voltage that arcs of higher volt-amperes can readily b extinguished when the resistor 26 is used than when it is not used. This latter feature is described and claimed broadly in the above-mentioned copending Blume circulating current but it also serves as an auto transformer which makes the voltage of the main conductor l4 halfway between the voltagegof the taps to which the contact fingers 3 and 4 are connected. When the contact fingers make engagement with the same tap the Position is known as the full cycle position. In this position there is substantially no voltage drop in the reactor I because there is no voltage to produce a circulat'-' in or magnetizing current and the electromag-" netic effects of the load current cancel each other.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a cam, means for selective- 1y rotating said cam about its axis in either direction, a pair of cam followers disposed on angularly displaced radii of said cam, separate switches actuated by each of said cam followers, and a third switch having actuating means disposed in the path of movement of members associated respectively with each of said cam folmeans actuated by said connections for opening the two remaining pairs of contacts after each of the first-mentioned two pairs of contacts is opened and for closing said two remaining pairs of contacts before each of said first-mentioned two pairs of contacts i closed.

4. In combination, a cam, means for rotating said cam, a pair of followers for said cam actuated in the same direction by the same portions of the face thereof and disposed on angularly displaced radii thereof, a pair of switches operated respectively by said cam followers, and a third switch actuated by each of said cam followers.

5. The combination as set forth in claim 4 in which said third switch opens after each of said pair of switches opens and closes before each of said pair of switches closes.

6. In combination, a cam, means for rotating said cam, a pair of followers for said cam actuated in the same direction by the same portions of the face thereof and disposed on angularly displaced radii thereof, a pair of switches operated respectively by said cam followers, a third switch actuated by each of said cam followers, and a circuit having a pair of effectively parallel branch conductors, the switches of said pair being connected respectively in circuit with said branch conductors, said third switch being connected between said branch conductors.

7. In combination, a cam having a normal position, means for selectively rotating said cam in either direction from said normal position, a pair of cam followers disposed on substantially diametrically opposite sides of said cam, a pair of normally closed switches connected respectively to said cam followers so that each of said switches will be pened and reclosed by a complete revolution of said cam, the order of operation of said switches being determined by the direction of rotation of said cam, a normally closed switch, a spring for biasing said last-mentioned switch closed, said last-mentioned switch having an actuating member so disposed in the path of movement of each of said pair of switches that the opening of either of said pair of switches is followed by the opening of said last-mentioned switch and the closing of either of said pair of switches is preceded by the closing of said lastmentioned switch.

8. In combination, a cam having a normal position, means for selectively rotating said cam in either direction from said normal position, a pair of cam followers disposed on substantially diametrically opposite sides of said cam, a pair of normally closed non-arcing duty switches connected respectively to said cam followers so that each of said switches will be opened and reclosed by a complete revolution of said cam, the order of operation of said switches being determined by the direction of rotation of said cam, a normally closed arcing duty switch, a, spring for biasing said last-mentioned switch closed, said last-mentioned switch having an actuating membe! so disposed in the path of movement of each of said pair of switches that the opening of either of said pair of switches is followed by th opening of said last-mentioned switch and the closing of either of said pair of switches is preceded by the closing of said last-mentioned switch.

9. In a load-ratio-control circuit of the double contact finger ratio adjuster type, in combination, separate sets of non-arcing duty selector contacts, a common set of arcing duty contacts, a single cam, a pair of cam followers on'angularly displaced radii thereof, said cam followers being connected to operate said sets of selector contacts respectively, and means responsive to the motion of either cam follower for controlling the operation of said arcing duty contacts.

10. In a load-ratio-control circuit of the double contact finger ratio adjuster type, in combination, separate sets of non-arcing duty selector contacts, a common set of multiple break arcing duty contacts, a single cam, a pair of cam followers on angularly displaced radii thereof, said cam followers being connected to operate said sets of selector contacts respectively,-and means responsive to the motion of either cam follower for controlling the operation of said arcing duty contacts.

JOSEPH X. MATHIEU. 

